The present invention relates to cells and populations thereof which can be used for treating CNS diseases.
Parkinson's disease is an age-related disorder characterized by progressive loss of dopamine producing neurons in the substantia nigra of the midbrain, which in turn leads to progressive loss of motor functions manifested through symptoms such as tremor, rigidity and ataxia.
The use of stem cells as a cellular source in cell replacement therapy for Parkinson's disease has been suggested. Stem cells have the ability to exist in vivo in an undifferentiated state and to self-renew. They are not restricted to cell types specific to the tissue of origin, and so they are able to differentiate in response to local environmental cues from other tissues. This capability of self renewal and differentiation has great therapeutic potential in curing diseases.
U.S. Patent Appl. 20050265983 to the present inventors teaches human dopamine synthesizing MSCs which express neuronal markers and transcription factors that characterize midbrain DA neuron following induction of neuronal differentiation.
As an alternative to a dopamine replacement strategy, cell therapy may be aimed at restoring or reestablishing the normal anatomy (connectivity) and physiology (appropriate synaptic contacts and functioning) of the striatum. In this instance, the grafted cells have to survive and possess morphological electrophysiological and functional dopaminergic properties.
Neurotrophic factors (NTFs) are secreted proteins that regulate the survival, functional maintenance and phenotypic development of neuronal cells. Alterations in NTF levels are involved in triggering programmed cell-death in neurons and thus contribute to the pathogenesis of Parkinson's and other neurodegenerative diseases.
One of the most potent NTF for dopaminergic neurons is called glial cell line-derived neurotrophic factor (GDNF). It is known to promote the survival of the dopaminergic neurons in the substantia nigra, promote neurite outgrowth, increase cell body size and also raise levels of TH. GDNF belongs to a family of proteins, related to the TGF-β-superfamily, currently consisting of four neurotrophic factors: GDNF, Neurturin (NTN), Persephin, and Artemin/Neublastin. These factors are known to serve as regulators of cell proliferation and differentiation.
Various cells type produce GDNF including glia cells (oligodendrocytes and astrocyte), neuroblastoma and glioblastoma cell lines. It has recently been shown that rat BMSCs cultured in DMEM supplemented with 20% fetal bovine serum, at passage 6 express GDNF and NGF [Garcia R, et al., Biochem Biophys Res Commun. 316(3):753-4, 2004].
Administration of GDNF directly into the brain has been shown to be effective in various animal models of PD. In addition, exposure of cells to GDNF prior to transplant has proven beneficial. For instance, grafting of 400,000 fetal dopaminergic neurons prior to transplantation significantly improved the rotational behavior of lesioned rats [Mehta V, et al., J Neurosurg. 1999 April; 90(4):804-6].
Various methods have been used to aid administration of GDNF into the brain including osmotic pumps, capsules and microspheres. Another approach for GDNF delivery is in vivo gene therapy. Bone marrow mesenchymal cells genetically engineered to express GDNF, transplanted into MPTP-lesioned mice, were able to protect nigral neurons as well as striatal fibers [Park, K., Neurosci. Res. 40: 315-323, 2001].
Glutamate is the main excitatory amino acid neurotransmitter in the human central nervous system (CNS). It plays a major role in synaptic plasticity, learning, development, cognitive functions and human behavior. However, if not properly controlled glutamate may lead to detrimental results. Prolonged exposure to glutamate leads to over stimulation of excitatory a.a receptors, a process culminating in neuronal cell death.
Regulation of glutamate levels near and within the synaptic cleft is primarily performed by astrocytes. When extracellular glutamate levels are high, astrocytes can remove it from the synaptic space. Glutamate uptake is facilitated mainly by high affinity excitatory a.a transporters, which insert Na+ and H+ into the cell, while removing K+ from the cell, thus enabling the transfer of glutamate into the cell against its electrochemical gradient. Although, the less common form of Na+ independent transport also occurs.
Accumulating evidence implicate glutamate toxicity in the pathophysiology of several acute neurodegenerative processes, mainly cerebral ischemia and traumatic brain injuries. Furthermore, it appears that glutamate toxicity participates in chronic neurodegenerative disorders such as Huntington's disease (HD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), epilepsy and Alzheimer's disease (AD).
Reducing extracellular glutamate levels around the susceptible neurons affected by glutamate toxicity in the different disease modules may halt the neurodegenerative progression. A possible approach to provide such neuronal protection is by transplanting cells capable of performing glutamate uptake adjacent to the endangered neurons. Adult human mesenchymal stem cells (hMSC) obtained from bone marrow, may vary well prove to be a viable source for such transplantations.
Several studies have shown that MSCs following exposure to different factors in vitro, change their phenotype and demonstrate neuronal and glial markers [Kopen, G. C., et al., Proc Natl Acad USA. 96(19):10711-6, 1999; Sanchez-Ramos, et al. Exp Neurol. 164(2):247-56. 2000; Woodbury, D., J Neurosci Res. 61(4):364-70, 2000; Woodbury, D., et al., J Neurosci Res. 69(6):908-17, 2002; Black, I. B., Woodbury, D. Blood Cells Mol Dis. 27(3):632-6, 2001; Kohyama, J., et al. Differentiation. 68(4-5):235-44, 2001; Levy, Y. S. J Mol Neurosci. 21(2):121-32, 2003].
WO2006/134602 teaches differentiation protocols for the generation of neurotrophic factor secreting cells.
WO2007/066338 teaches differentiation protocols for the generation of oligodendrocyte-like cells.
WO2004/046348 teaches differentiation protocols for the generation of neuronal-like cells.